The teenager joins a litany of players on the sidelines at Tynecastle, with such as Ryan Stevenson ruled out with a hamstring tear and Danny Wilson playing on despite shin splints.
Jamie Walker, the highly-rated attacking midfielder, is also struggling for fitness having gone off early at the weekend with an Achilles problem. His situation will be monitored ahead of a trip to face Celtic this weekend.
"Gary got a kick early doors in the Inverness match and now his leg has flared up," said Gary Locke, the Hearts manager. "It's another blow, we've certainly not had the best luck with injuries recently. The striking department is paper thin at the best of times."